This past Memorial Day, more than 1,000 teens swarmed the blocks around Lake Michigan in Chicago’s Hyde Park neighborhood. A resident described the scene: “Hundreds of people were walking and running down our street, jumping on top of cars, twerking, smoking blunts.” One group twerked on the top of a city bus. At about 9 pm, the Chicago Police Department closed Lake Shore Drive. As sirens wailed, the Hyde Park resident armed himself with bear spray to retrieve something from his car.